I can hear Occam chuckling over his copy of A Midsummer's Night Dream. What fools these mortals be! There is only one thing we need to understand - natural selection. Everything else is commentary.
This is not a plea to "social Darwinism," but to natural Darwinism, in which the survival of the species depends on its ability to rise above the Hobbesian war. The species and its selfish genes thrive through cooperation. It's simple plus-sum game theory. Because we are clever enough to kill ourselves off, we must be clever enough to find a reason not to.
Not only must we find that reason, we must find a way to communicate it to enough people to respect it. If it turns out that said reason is more subtle than the average brain can handle, we need to make up something more credible but with the same outcome. Enter God, the practically essential but otherwise unnecessary element in the explanation of why we shouldn't screw each other over.
Do we "own" our bodies? Sure, if that's the only way to get others to respect our right to live and keep what we produce. But it's all a fiction. We possess what we can defend, and we own what others respect. IF we respect others' autonomy and property, goods and services become available that would not become available but for respect for others' autonomy and property. It's a win-win game, nothing more. We can dress it up as one Kantian hand washing the other, but once we establish that a custom is economically optimal, everything else is window-dressing.
Maybe we will find a better way than respect for autonomy and property to achieve the goals laid out in the Preamble to the US Constitution, but until we do, the achievement of those goals seems to me a completely adequate reason for allowing as much autonomy and as much use of personal property as is consistent with those goals. Mario Cuomo famously said that politicians campaign in poetry and govern in prose. The Declaration of Independence, with its unalienable rights and endowments by our creator was campaign literature. The Constitution is the prose by which we are governed. Theology and libertarianism are campaigns. Natural selection and game theory rule.